Unstructured RNA is a substrate for tRNase Z.

Area of Science:

• Molecular Biology
• Enzymology
• RNA Processing

Background:

• tRNase Z is generally known for tRNA 3' maturation.
• The specific function of Escherichia coli tRNase Z is unclear as its gene is dispensable under normal conditions.

Purpose of the Study:

• To investigate if E. coli tRNase Z cleaves RNA substrates beyond pre-tRNAs.
• To characterize the cleavage activity of tRNase Z enzymes from various organisms on unstructured RNAs.

Main Methods:

• In vitro cleavage assays using recombinant tRNase Z enzymes from E. coli, Bacillus subtilis, and Thermotoga maritima.
• Testing cleavage efficiency on various unstructured RNA substrates.
• Determining metal ion requirements and kinetic parameters (rate constant, Kd) for enzyme-substrate complex formation.

Main Results:

• E. coli, B. subtilis, and T. maritima tRNase Z enzymes efficiently cleaved various unstructured RNAs in vitro.
• Specific cleavage site preferences were observed (e.g., after cytidine or before uridine for E. coli/B. subtilis).
• Eukaryotic tRNase Zs also cleaved unstructured RNA, but an archaeal tRNase Z did not.

Conclusions:

• E. coli tRNase Z possesses broader RNA cleavage activity than previously assumed, extending to unstructured RNAs.
• tRNase Z enzymes exhibit diverse substrate specificities and metal ion requirements across different species.
• The study suggests a potentially wider physiological role for tRNase Z enzymes in RNA metabolism.